Hitherto, as an actuator for opening and closing a valve body of a waste gate valve of a turbo charger of an engine, for example, a diaphragm type actuator is employed (for example, see Patent Document 1). The diaphragm type actuator includes an operation rod which is connected to a valve body, a diaphragm which drives the operation rod, a low pressure chamber and a high pressure chamber which are adjacent to each other with the diaphragm interposed therebetween in the axial direction of the operation rod, and a return spring which is disposed inside the low pressure chamber and urges the diaphragm.